This invention relates to an electrode tip dresser which dresses or reforms an electrode tip for a resistance welding machine, and to a cutter for use in the electrode tip dresser.
An electrode tip dresser is constructed in the following manner. Namely, a cutter is held by a cutter holder which is rotatably held in a dresser main body. The cutter holder is rotated while an electrode tip is urged against the cutter so that the front end portion of the electrode tip is cut and dressed by the cutter.
Conventionally, this kind of cutter comprises a central column-like block and a plurality of cutter blades which radially extend from the block. A flat portion which faces the front end surface of the electrode tip is made up by an end surface of the column-like block, and a rising portion around the flat portion is made up by each of the cutter blades. Cutting teeth for cutting the front peripheral portion of the electrode tip are formed in the rising portion. A plurality of cutting teeth which extend from the center of rotation of the cutter holder radially towards each of the cutter blades are formed in the flat portion so that the front end surface of the electrode tip can be cut by these plurality of cutting teeth. However, if the plurality of cutting teeth are formed in the flat portion, the cutting teeth at the central portion at which they meet each other form a chisel edge, resulting in a disadvantage in that the central portion at the front end surface of the electrode tip cannot be cut well.
In order to solve this kind of disadvantage, there is disclosed in Japanese Published Unexamined Utility Model Application No. 44949/1990 a cutter which has formed in the flat portion thereof a single piece of cutting tooth which extends from the center of rotation of the cutter holder towards a predetermined cutter blade.
If the cutting tooth to be formed in the flat portion is made up of a single piece, the rake face angle and the relief angle can be accurately provided also at that origin portion of the cutting tooth which coincides with the center of rotation, thereby improving the cutting quality at the center of the front end surface of the electrode tip. However, in this cutter, the origin portion of the cutting tooth is short of rigidity and is likely to break at that portion. If that portion is broken, the cutter cannot be used any more since there remains uncut the central portion of the electrode tip.